looked pretty interesting (loved the little animations). This doesn't seem like a bad idea: I do see the sensibility in using the same base propellant as in the 6inch guns, but ideally this would be a favorable candidate for liquid propellant/ElectroThermal Chemical gun technologies. Of course, just because the engineers have baited the hook, it doesn't mean the procurement fish will bite. Quite often, we lose the more desireable weapons systems because we got lickbag bureaucrats in too many positions of power and authority in DC. Such positions should not be filled by appointments, but rather actually test the candidates to see who is truly the most qualified for the job.
UDLP did much research with Denel of South Africa on 105mm artillery, because for a time the LEO 105 was suggested as armament for a new US 105 SPG system. It will be an interesting technology to watch. I would still argue: if we are going for it, develop a 120mm arty piece that can fire the same shells as the M1, just with a different propellant option. The Swedish CD80/KARIN, a Bofors product, was a 120mm coastal system using an FH-77 mount on an articulated chassis (Volvo), can supposedly reach 30km..

It would seem to me anytime theres a liquid involved you have a fire hazard,explosian hazard due to leaks.Isnt that one reason theyre doing away with liquid propulsion on rockets?going by what doggtag said.

Liquid tends to be harder to handle, as it leaks when compromised: with toxic rocket fuel this is usually a problem. It will probably be the same with propellants which could ignite in a closed confines of a tank or self-propelled gun, or even in the breech. The "powder bags" are filled with solid propellants, or are they actually liquid? I'm not quite sure where the liquid propellant discussion came from: but then again, I have no military experience (not to mention artillery branch).
In any case, the need to shoot 120mm tank shells from arty: wouldn't it tempt arty commanders to pack tank rounds and think that they are tanks? The transition would mean the disposal of lots of 105mm rounds, as I am unsure if there are any 105mm artillery pieces left: are they all 155mm already?

Some of the technology behind LP guns does utilize fire-sensitive fuel. But then again, if your vehicle gets smacked by a sufficient round, it won't mean jack if you're packing solid grain propellant charges or a tank of fluid (few SP systems carry the ammo protection that MBTs have). And AFVs have been carrying flammable fuel since WW1 (deisel will light up just as well when an HE round smacks you). The Crusader was anticipated to use solid propellant ignited by a laser ignition system, which in time would have likely progressed to the liquid propellant, whose combustion can be controlled at a far better rate than solid, allowing for better ballistics performances. Some of the ideas behind Electro Thermal Chemical propellant suggest using a very high current to ignite an otherwise "insensitive" propellant fuel (which would not normally ignite under open flame). Varying the amount of LP and current defines the burn characteristic and resulting ballistic performances. It is still being debated in circles as to whether a tank of propellant and rack of shells will be safer or not over a rack of shells and a rack of charges. The risk of propellant leaks would be no worse than regular fuel leaks.
As far as getting license for the Denel equipment and type-classification into US service, I expect the object of the collaboration was to enable a US defense contractor to get some better insight into higher performance 105mm artillery. Perhaps some of the tech behind the V2C2 cannon that originated this thread has come about because of the collaboration.
And as far as 120mm arty firing tank rounds... that was not my intention. I meant that a 120mm round can pack more lethality than a 105mm, yet is lighter and more "man friendly" (portability of slinging rounds around by hand) than the 100pound 155mm shells. I don't believe that just because "there is a big supply of that caliber of ammo" is justification to keep any weapon system in use (perhaps it's time for more training missions to fire off all the older stocks of ammo that won't be getting "recycled or demilitarized"). If a better ballistically and higher lethality 120mm shell can be developed over the 105mm, then why keep the 105? For people who would argue that everything should be 155mm now, there was claim by Denel that their newer 105mm ammo for the LEO was even as lethal as many earlier generations 155mm ammo still in use. So since MBTs can fire 120mm general support ammo, why not adjust the commonality across the board? Supposedly, the older M68 series 105s could fire much the same shells, but with a different propellant system, as some of the US's 105mm arty. And I don't suggest giving sabot rounds to artillery groups. A couple of 120mm Israeli-type LAHATs or comparable rounds per gun would be suitable for any self-defense requirement, but mostly just pursue the same load-out as any other SP gun. UDLP several years ago made a variant of M109 for Egypt that utilized their 122mm ex-Soviet artillery. A considerable increase in ammo over the 155mm formerly installed was a welcome addition. A long range 120mm system would afford the same, as could the 105 (but I'm not trying to imply we "recycle" older M109s laying around into them, although we could).
This whole artillery argument (105/120/122/152/155) needs to be generally overhauled: long range barrages will be a thing of the past as newer precision rounds are fielded. And troops will be engaged with air-burting cluster rounds, requiring again less shells fired for a given engagement. It may be realized that, effectively, we do not really NEED the 155mm class of guns. A course correcting guided shell can be packaged down to as small as 40mm (it was done by Vought in the US in 1986). We would need to evaluate just what caliber gives us the most favorable capability against the targets we are trying to eliminate, as opposed to taking any particular caliber and seeing what all we can shoot with it. The US has only fairly recently realized the value of 120mm mortars (the 81 sometimes wasn't enough, and the older 4.2s were pretty much gone). Perhaps a re-evaluation of our artillery requirements is in order.
Pending another outbreak in large MBTs, it is a safe bet that we won't be needing to upgrade to the 140mm class guns. Perhaps we have reached another commonaliy niche with MBTs and artillery both launching 120mm ammo.
Sweden has invested a decent chunk in its coastal batteries, including the 120mm L62 ERSTA gun systems. Even though they are moving towards an all 155mm force (most likely, jumping on the boat everyone else has jumped on), a 120mm round is still sufficiently dangerous to any naval vessel or surface target (a generic 120 HE round does have sufficient blast to trash even an MBT if the impact point is right).
Unless an all-out conflict with someone massive (China, in example) happens, massed barrages of anti-infantry artillery will not be needed. It's time we finally abandon our Cold

from further information searches, I see that there are developments of polymer-based "blocks" of stable (fire resistant?) solid propellant that are being researched for the electrothermal chemical guns. Such propellant would again alleviate any concerns of fuel leakage in a liquid propellant system..

I am always amazed (amused?) when someone claims that their new shell is equal in performance to an existing product of larger caliber. Is it true? Possibly but it is based on the fact that the newer product uses newer technology. They conveniently overlook the fact that if the same technology is applied to the larger shell it will, once again, become superior.